[May 01, 2014]
(Reuters) —Merrimack Pharmaceuticals Inc said its
lead experimental cancer drug when used as a combination improved
the overall survival rate in patients with metastatic pancreatic
cancer, doubling its shares in premarket trading.

Merrimack said a combination of its drug, MM-398,
and two others showed an overall survival of 6.1 months, compared
with 4.2 months shown by the other two drugs alone.

The company said on Thursday it would apply for a U.S. marketing
approval for the combination this year.

The late-stage study was testing the drug in patients who were
earlier treated with chemotherapy drug gemcitabine.

The trial tested MM-398 in combination with another chemotherapy
drug 5-fluorouracil (5-FU) and leucovorin, which helps enhance
5-FU's effectiveness.

Merrimack said its drug showed an overall survival of 4.9 months
when used alone, which was not statistically significant.

The company said the most common serious adverse events in patients
given the combination were an abnormally low count of a type of
white blood cells, fatigue, diarrhea and vomiting.

Merrimack said patients taking only MM-398 experienced a higher
level of adverse events than those who received the drug
combination.

About 46,420 new cases of pancreatic cancer will occur in the United
States in 2014, according to the American Cancer Society.